﻿<!DOCTYPE html>
<html>
	<meta charset="UTF-8"/>
	<head>
		<script>
			//求圆的面积
			
			var circleArea = function(radius){
				return 3.1415926*radius*radius;
			}
			var res = circleArea(5);
			
			//console.log(res);
			//alert(res);
			//document.write(res);
			
			
			//编写函数，判断一个字符串的内容是不是纯数字
			function isANum(str){
				if(!Number(str)){
					return false;
				} 
				return true;
			}
			
			var s = isANum("123d456");
			console.log(s);
		</script>
	</head>
	<body>
		
		<button>点我</button>
	</body>	
</html>











